Cyanine dyes derived from 2-methylthiazole derivatives



Patented Feb. 28, 1939 UNITED STATES OFFICE CYANINE urns DER V D RROM 2=METHL- THIAZOLE nna vnrr vas poration of Delaware No Drawing. Original application March 25,

1932, Serial No. 601,290. Divided and this application January 30,

3 Claims.

This application is a division of our co -pending application Serial No. 601,290 filed March 25, 1932, which claims photographicelements containing the dyes herein described.

5 Qur present invention relates to a new composition of matter, more particularly to cyanine dyes, and one of its objects is to provide a dye capable of imparting improved and selective color sensitization to photographic emulsions. Another ob- J'ect is to extend with relative uniformity the sensitivity of the emulsion to light in a wide range of the longer Wave lengths, especially to those wave lengths in the vicinity of the red and green regions of the spectrum. Other objects will plainly appear from the detailed description prese ted here To enable those skilled in the art to use our invention, we will as an illustration describe its preferred embodiment with the understanding that modifications may be presented without departing from its broader spirit and scope.

To efficiently intensify the speed and color sensitivity of an emulsion to light in the above described po-rtions of the spectrum, we have discovered a type of novel cyanine dyes derived from certain thiazole bases represented diagrammatically by the following general formula:

X-CN\ H C OHa Y-CS/ wherein X and Y are used to designate substituents. ,Preferred thiazole bases from which our novel type of .cyanine dyes is derived, are those bases obtained by varying the groups in the four and five positions of the aforementioned general formula. We are thereby afforded bases represented by the following formulae:

1934, Serial No.- 709, 48

wherein R represents any alkyl group, or substituted alkyl group.

by Hantzch in Annalen, No. 250, page 2697 As will be further shown, our dyes are derived as a result of substituting a methyl group in the two position of the aforementioned formula, in addition to varying therein the groups in the four a fiv os t on ;In general we prefer to make our novel dyes by first converting the above mentioned methyl thiazole bases to ,quaternary compounds, preferably by heating them with ethyl iodide or ethyl u n -sul h na e- These quaternary compounds may then ;be converted to novel cyanine dyes which will be grouped and described in the three following correlated examples: (A) Thiccar-bocyanines, (l3) Pseudocyanines, (C) Dyes e ated t ocvanims- To further explain our invention we will describe various preferred illustrations in each of the aforementioned examples of dyes made from our herein described thiazole bases, first using Base I (diphenyl-methyl-thiazole), although the related bases II, III, or IV, may be used whenever described.

. l'l the following formulae for our novel cyanine CfiFCaN dyes ,given under Examples A, B, C, We use It to represent any alkyl or .substituted alkyl group and o.m-os Xto representa suitable acid radicle such as the w H iodide radicle or the para-toluene-sulphonate radicle.

o-orn E m l 4-. hio a b H,C-S One of the preferred thiocarbocyanines is de- ,50 m rivedfrorn Base I inthe following manner: The ethiodide of -2-methyl-4,5- dipheny1 thiazole is preferably heated in pyridine solution with a C CH3 small amountof ethyl orthoformate. The dye forms and on cooling it precipitates. It is then ,55 HFF"? filtered and is recrystallized from alcohol.

It is then dissolved in alcohol, and subsequently added to the photographic emulsion.

More specifically, this preferred thiocarbocyanine is derived from Base I in the following manner: Two grams of the ethiodide of 2-methyl- 4,5-diphenyl thiazole (or an equivalent amount of some other quaternary salt such as 2.2 grams of the p-toluene sulphonate) and 4 grams of ethyl o'rthoformate and 15 grams of dry pyridine, in a dry flask with a reflux condenser attached, are heated to boiling. The mixture is allowed to reflux for one hour. A blue dye gradually forms. The flask is allowed to stand overnight in a cool place, and the precipitated dye is filtered and washed with ether. It is then recrystallized from alcohol. This dye, added to the emulsion, confers an extra sensitivity to it, with a maximum Other novel thiocarbocyanine dyes may be derived from thiazole Base Number II. One of such dyes is the ethiodide, and is represented by the This dye may be made exactly like the dye described in Example A except that instead of 2 grams of the ethiodide of Base I, one uses 1.6 grams of the ethiodide of Base II. The resulting dye confers an extra sensitivity to the emulsion when added to it as described in Example A, except that the sensitivity has a maximum at approximately 590 and extends to 650.

In a like manner, by employing the herein described thiazole Base III, we derive additional and novel thiocarbocyanine dyes, among which is the dye represented by the following formula:

For example, if, in Example A, one uses instead of 2 grams of the ethiodide of Base I, an equivalent amount of the ethiodide of Base III, one obtains a blue dye which confers a moderate extra sensitivity to the emulsion, with maximum at 580 and extending to 630.

An additional and novel thiocarbocyanine dye may be derived in a like manner from Base IV in the following manner: The ethiodide of 2-methyl 4 phenyl 5 methyl, thiazole is added in pyridine solution with a small amount of ethyl orthoformate. The dye forms and on cooling and diluting with ether it precipitates. It is purified by recrystallization from alcohol. It is then dissolved in alcohol and a small amount of the dye is added to a photographic emulsion, preferably at some time before the emulsion is coated on its support. This will provide the emulsion with a greatly increased sensitivity reaching a maximum at 600mu. This dye is represented by the For example, in Example A, if one uses instead of the ethiodide of Base I, an equivalent amount of the ethiodide of Base IV, one obtains a blue dye which confers an extra sensitivity to a photographic gelatino-silver halide emulsion, with maximum at approximately 595 and extending to 620.

Example B.-Pseudocycmines One of our prefered pseudocyanines is derived treated with .55 grams of potassium hydroxide Boiling is condissolved in absolute alcohol. tinued for fifteen minutes, and a red dye gradually forms. On cooling, it crystallizes. It may be recrystallized from alcohol. This dye may be represented by the following formula:

or by the formula:

either designation indicating the same dye because the position of the acid radical is uncertain. The formula might also be written:

Two grams of the scribed above. This dye is represented by the following formula:

Example C.--Dyes related to isocyanmes 4,5-diphenyl thiazole and 1.4 grams of quinoline ethiodide are dissolved in 50 cc. of boiling alcohol and treated with .28 gram of potassium hydroxide dissolved in alcohol. The mixture is maintained at the boiling point for fifteen minutes, and a red dye is formed. It may be purified by recrystallization from alcohol. This dye is represented by the following formula:

We have found that our invention has provided a type of novel oyanine dyes that has enabled us to obtain greatly improved color balance in the ultimate image, by the incorporation of one or more of our dyes in a photographic emulsion. These dyes act with marked efiiciency to uniformly and selectively extend the sensitivity of prior panchromatic emulsions to light in a wide range of the longer wave lengths, especially in the vicinity of the red and green regions of the spectrum, without conferring any abrupt or over emphasized increase of the sensitivity in any relatively restricted region of the spectrum that would tend to distort or destroy the desired color balance in the final photographic image.

Numerous dyes that are the allied or related equivalents of those dlsclosed'herein may be used without departing from our invention and it is clearly contemplated that such equivalents, or modifications thereof, as well as the use of such dyes as sensitizers for photographic emulsions, fall within the intent and scope of the appended claims.

What we claim as our invention and desire to be secured by Letters Patent of the United States 1s:

1. A thiopseudocyanine dye having the following general formula:

in which R represents alkyl, and X is a halogen atom.

2. A methine cyanine dye having the following ing general formula:

wherein both Y and Z represent benzene nuclei,

R represents alkyl, X represents the negative radical of an acid, A represents a radical selected from the group consisting of phenylene and naphthylene, and the methine carbon atom is linked in one of the 2- and 4-positions.

3. A thiopseudocyanine dye having the following general formula:

where R represents alkyl and X represents a halogen atom.

GEORGE A. DAWSON. EDMUND B. MIDDLETON. 

